MESOSCALE DISCUSSION 1100
   NWS STORM PREDICTION CENTER NORMAN OK
   0709 PM CDT SAT JUN 13 2009
   
   AREAS AFFECTED...ERN PA...CNTRL MD...NRN VA...D.C.
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 140009Z - 140115Z
   
   A MARGINAL WIND/HAIL THREAT SHOULD PERSIST FOR AN HOUR OR TWO PRIOR
   TO ONGOING TSTMS ENCOUNTERING A RAIN-COOLED AIR MASS FARTHER EAST. A
   WW WILL LIKELY NOT BE NEEDED.
   
   ISOLATED TO SCATTERED TSTMS CONTINUE TO DEVELOP ALONG A WEAK SURFACE
   TROUGH AND AN OUTFLOW BOUNDARY FROM E-CNTRL PA THROUGH CNTRL MD INTO
   NRN VA...DOWNSTREAM OF A SHORT WAVE TROUGH CROSSING THE LOWER GREAT
   LAKES. 00Z SUBJECTIVE SURFACE ANALYSIS PLACED THE TROUGH AXIS FROM
   NEAR MSV TO LYH...WITH A WELL-DEFINED OUTFLOW BOUNDARY ALONG THE WRN
   SHORES OF CHESAPEAKE BAY AND INTERSECTING THE TROUGH AROUND 40 W
   ABE. A RELATIVELY SMALL AREA OF MODEST SURFACE-BASED INSTABILITY
   REMAINS WEDGED BETWEEN THESE TWO BOUNDARIES AND WILL CONTINUE TO
   SUPPORT A MARGINAL WIND/HAIL THREAT GIVEN EFFECTIVE SHEAR AROUND 35
   KT. AS ACTIVITY LIKELY TRAVERSES AND REINFORCES THE OUTFLOW
   BOUNDARY...OVERALL AREAL EXTENT OF SEVERE POTENTIAL SHOULD DIMINISH
   THROUGH THE EVENING.
   
   ..GRAMS.. 06/14/2009
   
   
   ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...
   
   LAT...LON   39037779 40217677 40967607 41257542 41077532 40537588
               39467640 38867631 38347639 38067674 37967739 38077794
               38357830 39037779